Electric variable pitch log



y 1, 1940. E. GRANAT 2,201,896

. ELECTRIC VARIABLE PITCH LOG Filed Nov. 5,- 1938 2 Sheets-Sheet 1 FIGURE l E. GRANAT ELECTRIC VARIABLE PITCH LOG May 21; 1940.

2 Sheets-Sheet 2 Filed Nov. 5, 1938 FIGURE 5- FIGURE 5 j FIGURE 4 Inve Patented May 21, 1940 UNITED STA ES g 2.201.890 ELECTRIC vsamam rnrcn LOG Elie Granat, Paris, France, assignor of one-half to Oomnazni e des Forges ct "Am 'de la Marine et dflomecourt, Paris, France, a company of France Application November 5, 193a, Serill No. 239,103

In France November 23, 1931 1 Claim.

Among the logs used for determining the speed of airplanes with reference to the atmosphere some are based on the property of propellers of rotating at speeds which are functions of their linear speed of displacement along their axis of rotation. Consequently, logs of this type include generally a detecting partconstituted by a vane wheel comprising one or more helical surfaces, the movement of which is transmitted to an in-.

0 dating part constituted by a speedometer.

However, when such logs are mounted on air-. planes, the calibration made at the blower plant may appear untrue byreason of the necessity of arranging said logs in the vicinity of thewings or of the fuselage of the airplane, thesurfaces of which produce a slight'deformation of the air stream-lins'acting on the vane wheel; one is thus led either to provide the readings on the v speedometer with a predetermined coeflicient the value of which is ascertained experimentally during-the tests, or else to modify the existing ratio between the movementof the vane wheel and that of the speedometer.

The first method which consists in providing with a coemcient the values appearing on the indicator is but little practical. The secondmethod meets with diillculties in the execution of means for continuously varying the ratio existing between the number of revolutions of the i vanewheel and that of the shaft driving the mmounting-the apparatus on the airplane. This generally slight correction of the pitch of the impeller has for its result to provide the values appearing on the indicator with a substantially constant coefficient which is equal to the coefllcient of modification of'pitch of the cane! A wheel.

Although this coeiilcient does not seem to be absolutely constant at all speeds, it is sufllcient in practice to choose the value corresponding to the'normal cruising speed of they aircraft in order that the pilot may make satisfactory use of the indications given by the log. I

65 The invention is applicable on any aircraft,

whatever may be its type, on which the apparat is mounted.

Appendeddrawings show the invention as applied to a log of the synchronous type, wherein the vanewheel acts on a transmitter which ac- 5 tuates synchronously an electrical receiver controlling mechanically an indicator of instantaneous speeds. Fig: 1 is a general view of the arrangement.

Fig.3 shows in detail the variable pitch vanewheel. 1 P18. 3 is a detail view of the'receiver.

Figs. 4 and 5 are views ,of the transmitter proper. V k

In the form of execution illustrated the vanewheel I shown in Fig. 1 controls a transmitter 2 through a suitable mechanism 3. This transmitter actuates at a distance a synchronous electric receiver 4 the shaft. of which drives a speedometer of any type. including a scale of 10 instantaneous speeds. The speedometer may of course include or not include totalizers giving out the number of revolutions.

Fig. 2 shows diagrammatically by way of example a form of execution of the transmitter with 2 a variable pitch vanewheel. This transmitter comprises a stationary casing ll an extension of which is formed by a movable streamlined rotary part I: which forms the hub on which are arranged a certain number of blades l3 con- 0 stituted each by a portion of helical surface having a given pitch. These blades may move round their axes and the variation of pitch is obtained by a slight rotation round their axes. This displacement maybe obtained by any known me- 5- chanical means such as that shown byway of example in Fig. 2 wherein each blade is provided with a bevel pinion I4 and the whole system of pinions I4 is' controlled by a bevel pinion IS the rotation'of which is controlled fromthe outside 40 of the movable casing I! through rotation of the spindle ll rigidly secured to said bevel pinion i5 and providedwith a squared end and a lock nut I.

The movable [2 includes an extension 45 forming a spindle 36 adapted to rotate inside the stationary casing II and controlling thetransmitter properll.

In the form of ex cution illustrated by way of example in Figs. 4 and 5, the transmitter is con- The segments 24 and II are electrically connected to contacts at the ends of the shaft by means of conductors extending longitudinally of the hollow shaft IS. The segments 24 and 25 are fed by the D. C. mains 26 through the brushes 21 and 28 cooperating with corresponding contacts connected with the segments and arranged respectively at'the two ends of the hollow shaft l9 and this arrangement is devised with a view to reducing to a minimum the resistant torque produced by friction. On the cylindrical periphery of the segments 24 and 25 are arranged three equally spaced stationary brushes 29-30 and 3|, connected with the transmission wires 8. The arrangement requires consequently, beyond the two feed wires, three line wires between the transmitter and the receiver.

Fig. 3 shows with further detail the indicator. The latter comprises a synchronous receiver 4 constituted for instance by a stator 5 forming the fleldpiece and by a polyphase rotor 6 which receives the current from the transmitter 2 through the feed rings I and the wires 8. The shaft 9 of the synchronous receiver operates a speedometer Ill of known type including a totalizer if desired.

By reason of the extremely reduced friction in the abovedescribed transmission system, the propeller 1 assumes a speed of rotation which is a practically linear function of its speed of displacement along the air stream. This movement is transmitted to the shaft is of the transmitter which produces a continuous distribution of the potentials from the feed mains 26 into the wires of the transmission line 4 and consequently into the polyphase winding of the synchronous receiver 6.

The working diagram of this transmission shows that each shifting through one twelfth of a revolution of the transmitter shaft l9 produces an equal rotation of the rotor i of the synchronous receiver 4. The movement continues thus in synchronism and in a continuous manner whatever the speed of the transmitter may be.

The synchronism between transmitter and receiver is ensured even in the case of a temporary disconnection between the mains and the receivers; synchronism is resumed as soon as the receivers are fed as the receiver is the seat of a rotary field produced by the rotation of the transmitter; the receiver starts then as an asynchronous motor and comes into step so as to move synchronously with the transmitter.

The windings of the receiver are designed in a manner such that the maximum speed allowed of the vanewheel until the values read correspond to the values calculated. The correction made is of course valid for a given speed which is preferably the normal cruising speed of the airplane.

These pitch adjusting means may be completed by a pointer 35 moving over a stationary scale on the hub II. This scale may either be empirically graduated or express the correction in percents oi the pitch.

What I claim is:

An electric log for aircrafts comprising a speedometer, a receiver controlling the speedometer, a transmitter including a hollow rotary shaft, a contact carried at each end of said shaft, stationary means for feeding current to said contacts, a distributor secured to the rotary shaft and constituted by conducting segments and insulating parts separating the segments, means arranged longitudinally of the rotary shaft for connecting the contacts thereof to the corresponding conducting segments, stationary brushes adapted to engage said conducting segments, polyphase wires connecting said brushes with the receiver for controlling the same, and a vanewheel adapted to rotate at a speed depending on the speed of flight of the aircraft and comprising at least one variable pitch blade and a rotary shaft therefor drivingly connected with the hollow rotary shaft of the transmitter.

ELIE GRANAT. 

